With reference to this type of a conventional power amplifier, there has since been known a configuration disclosed in JP-A No. 76954/2002 (Patent Document 1). FIG. 4 is a block diagram showing the configuration. A power amplifier 10 comprises a differential amplifier 11, a single amplifier 12, and a capacitor 13, and the output side of the differential amplifier 11 is coupled with the input side of the single amplifier 12 via the capacitor 13. In FIG. 4, reference numeral 1 denotes an antenna, 2 a filter, 3 an isolator, and 4 a coupler.
Further, as a structure of another conventional high frequency power amplifier, a high output voltage control oscillator has been disclosed in JP-A No. 164797/2002 (Patent Document 2). FIG. 5 is a block diagram thereof. The high output voltage control oscillator has a configuration where there are provided an input terminal 110 to which a control voltage is delivered, a voltage control oscillator 14 to which the control voltage delivered to the input terminal 110 is supplied, a power amplification unit 17 which an output of the voltage control oscillator 14 is supplied to, and is made up of a plurality of amplification circuits 19 to 21, connected in series, and an output terminal 18 to which an output of the power amplification unit 17 is supplied, and the voltage control oscillator 14, and at least the amplification circuit 19 in the initial stage of the power amplification unit 17 are made up of a balanced amplification circuit, respectively, while a balanced-to-unbalanced conversion circuit (balun) is provided inside the power amplification unit 17. In FIG. 5, reference numeral 15 denotes an output terminal of the voltage control oscillator, 16 a matching circuit, 120 a resonance circuit, 130 the balanced amplification circuit, 22 a power control terminal, and 23 a package.    [Patent Document 1] JP-A No. 76954/2002    [Patent Document 2] JP-A No. 164797/2002